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/*! \file
    \brief Templates implementing computing the addresses of loading small
    vectors from the global memory.
*/

#pragma once

#include "cutlass/cutlass.h"
#include "cutlass/array.h"
#include "cutlass/coord.h"
#include "cutlass/layout/pitch_linear.h"
#include "cutlass/layout/matrix.h"
#include "cutlass/layout/tensor.h"
#include "cutlass/matrix_coord.h"
#include "cutlass/matrix_shape.h"
#include "cutlass/tensor_ref.h"

////////////////////////////////////////////////////////////////////////////////

namespace cutlass {
namespace transform {
namespace threadblock {

////////////////////////////////////////////////////////////////////////////////

/// PredicatedVectorAccessIterator
///
template <typename Shape, typename WarpShape, typename Element, typename Layout,
          int ElementsPerAccess>
class PredicatedVectorAccessIterator;

////////////////////////////////////////////////////////////////////////////////

/// Vector access iterator specialized for vectors, e.g. scale and bias
/// Thread arrangements are for TensorOps
///
template <typename Shape_, typename WarpShape_, typename Element_,
          int ElementsPerAccess>
class PredicatedVectorAccessIterator<Shape_, WarpShape_, Element_,
                                     layout::PitchLinear, ElementsPerAccess> {
public:
    using Shape = Shape_;
    using WarpShape = WarpShape_;
    using Element = Element_;
    using Layout = layout::PitchLinear;

    using Index = typename Layout::Index;
    using LongIndex = typename Layout::LongIndex;

    using TensorRef = TensorRef<Element, Layout>;
    using TensorView = TensorView<Element, Layout>;
    using TensorCoord = typename Layout::TensorCoord;

    using ConstPointer = const Element*;
    using NonConstPointer = typename platform::remove_const<Element>::type*;

    //  static int const kElementsPerAccess = 128 / sizeof_bits<Element>::value;
    static int const kElementsPerAccess = ElementsPerAccess;
    static int const kThreads = 32;
    static int const kRowsPerIteration = 8;
    static int const kThreadsPerRow = kThreads / kRowsPerIteration;
    static int const kThreadsPerRowMask = 0x3;
    static int const kIterations =
            WarpShape::kContiguous / (kThreadsPerRow * kElementsPerAccess);
    static int const kWarpCountStrided = Shape::kStrided / WarpShape::kStrided;

    using AccessType = AlignedArray<Element, kElementsPerAccess>;

private:
    /// Internal pointer type permits fast address arithmetic
    using BytePointer = char*;

private:
    //
    // Data members
    //

    /// Internal pointer to first access of tile
    BytePointer pointer_;

    /// Extent of tensor
    TensorCoord extent_;

    /// pointer offset of each thread
    TensorCoord thread_offset_;

    /// iteration index
    LongIndex iteration_;

public:
    /// Constructs a vector access iterator
    CUTLASS_HOST_DEVICE
    PredicatedVectorAccessIterator(
            /// Pointer to the start of the vector
            ConstPointer pointer,
            /// Extent of vector
            TensorCoord extent,
            /// ID of each participating thread
            int thread_id,
            /// ID of each participating warp
            int warp_id,
            /// Initial offset of threadblock
            TensorCoord const& threadblock_offset)
            : pointer_(reinterpret_cast<BytePointer>(
                      const_cast<NonConstPointer>(pointer))),
              extent_(extent) {
        int warp_offset =
                (warp_id / kWarpCountStrided) * WarpShape::kContiguous;

        // Per-thread offset in logical coordinates of tensor

        thread_offset_ = threadblock_offset + TensorCoord(warp_offset, 0) +
                         TensorCoord((thread_id & kThreadsPerRowMask) *
                                             kElementsPerAccess,
                                     0);

        set_iteration_index(0);
    }

    /// Construct a PredicatedVectorAccessIterator with zero threadblock offset
    CUTLASS_HOST_DEVICE
    PredicatedVectorAccessIterator(
            /// Pointer to start of vector
            ConstPointer pointer,
            /// Extent of vector
            TensorCoord extent,
            ///< ID of each participating thread
            int thread_id,
            /// ID of each participating warp
            int warp_id)
            : PredicatedVectorAccessIterator(pointer, extent, thread_id,
                                             warp_id, make_Coord(0, 0)) {}

    /// Overrides the internal iteration index
    CUTLASS_HOST_DEVICE
    void set_iteration_index(int index) { iteration_ = index; }

    /// Advances an iterator along logical dimensions of matrix in units of
    /// whole tiles
    CUTLASS_DEVICE
    void add_tile_offset(TensorCoord const& tile_offset) {
        thread_offset_ =
                thread_offset_ +
                TensorCoord(WarpShape::kContiguous * tile_offset.contiguous(),
                            0);
    }

    /// Returns a pointer
    CUTLASS_HOST_DEVICE
    AccessType* get() const {
        return reinterpret_cast<AccessType*>(
                pointer_ + ((thread_offset_.contiguous() +
                             iteration_ * kThreadsPerRow * kElementsPerAccess) *
                            sizeof_bits<Element>::value / 8));
    }

    /// Increment and return an instance to self.
    CUTLASS_HOST_DEVICE
    PredicatedVectorAccessIterator& operator++() {
        ++iteration_;
        if (iteration_ >= kIterations)
            iteration_ = 0;

        return *this;
    }

    /// Increment and return an instance to self.
    CUTLASS_HOST_DEVICE
    void advance() { add_tile_offset(TensorCoord(1, 0)); }

    /// Increment and return an instance to self.
    CUTLASS_HOST_DEVICE
    PredicatedVectorAccessIterator operator++(int) {
        PredicatedVectorAccessIterator self(*this);
        operator++();
        return self;
    }

    /// Returns whether access is valid or not
    CUTLASS_HOST_DEVICE
    bool valid() {
        return ((thread_offset_.contiguous() +
                 iteration_ * kThreadsPerRow * kElementsPerAccess) <
                extent_.contiguous());
    }
};

////////////////////////////////////////////////////////////////////////////////

/// Specialization of PredicatedVectorAccessIterator for row-major data.
///
template <typename Shape_, typename WarpShape_, typename Element_,
          int ElementsPerAccess>
class PredicatedVectorAccessIterator<Shape_, WarpShape_, Element_,
                                     layout::RowMajor, ElementsPerAccess> {
public:
    using Shape = Shape_;
    using WarpShape = WarpShape_;
    using Element = Element_;
    using Layout = layout::RowMajor;

    using Index = typename Layout::Index;
    using LongIndex = typename Layout::LongIndex;

    using TensorRef = TensorRef<Element, Layout>;
    using TensorView = TensorView<Element, Layout>;
    using TensorCoord = typename Layout::TensorCoord;

    using ConstPointer = const Element*;
    using NonConstPointer = typename platform::remove_const<Element>::type*;

    using UnderlyingIterator = PredicatedVectorAccessIterator<
            layout::PitchLinearShape<Shape::kColumn, Shape::kRow>,
            layout::PitchLinearShape<WarpShape::kColumn, WarpShape::kRow>,
            Element, layout::PitchLinear, ElementsPerAccess>;

    using AccessType = typename UnderlyingIterator::AccessType;
    static int const kElementsPerAccess =
            UnderlyingIterator::kElementsPerAccess;
    static int const kRowsPerIteration = UnderlyingIterator::kRowsPerIteration;
    static int const kThreads = UnderlyingIterator::kThreads;
    static int const kIterations = UnderlyingIterator::kIterations;

private:
    //
    // Data members
    //

    /// Underlying pitch-linear tile iterator
    UnderlyingIterator iterator_;

public:
    /// Constructs a TileIterator from its precomputed state, threadblock
    /// offset, and thread ID
    CUTLASS_HOST_DEVICE
    PredicatedVectorAccessIterator(
            ///< Pointer to the start of the vector
            ConstPointer pointer,
            ///< Extent of tensor
            TensorCoord extent,
            ///< ID of each participating thread
            int thread_id,
            ///< ID of each participating warp
            int warp_id,
            ///< Initial offset of threadblock
            TensorCoord const& threadblock_offset)
            : iterator_(pointer,
                        layout::PitchLinearCoord(extent.column(), extent.row()),
                        thread_id, warp_id,
                        layout::PitchLinearCoord(threadblock_offset.column(),
                                                 threadblock_offset.row())) {}

    /// Construct a PredicatedVectorAccessIterator with zero threadblock offset
    CUTLASS_HOST_DEVICE
    PredicatedVectorAccessIterator(
            ConstPointer pointer,  ///< Pointer to the start of the vector
            TensorCoord extent,    ///< Extent of tensor
            int thread_id,         ///< ID of each participating thread
            int warp_id            ///< ID of each participating warp
            )
            : PredicatedVectorAccessIterator(pointer, extent, thread_id,
                                             warp_id, make_Coord(0, 0)) {}

    /// Overrides the internal iteration index
    CUTLASS_HOST_DEVICE
    void set_iteration_index(int index) {
        iterator_.set_iteration_index(index);
    }

    /// Advances an iterator along logical dimensions of matrix in units of
    /// whole tiles
    CUTLASS_HOST_DEVICE
    void add_tile_offset(TensorCoord const& tile_offset) {
        iterator_.add_tile_offset({tile_offset.column(), tile_offset.row()});
    }

    /// Returns a pointer
    CUTLASS_HOST_DEVICE
    AccessType* get() const {
        return reinterpret_cast<AccessType*>(iterator_.get());
    }

    /// Advances to the next tile in memory.
    ///
    /// The first time this method is called, predicates are updated, and the
    /// iterator's internal pointer is reverted to the first "steady state"
    /// tile. Subsequent calls are lightweight and must only update the internal
    /// pointer.
    CUTLASS_HOST_DEVICE
    PredicatedVectorAccessIterator& operator++() {
        ++iterator_;
        return *this;
    }

    /// Advances to the next tile in memory.
    ///
    /// The first time this method is called, predicates are updated, and the
    /// iterator's internal pointer is reverted to the first "steady state"
    /// tile. Subsequent calls are lightweight and must only update the internal
    /// pointer.
    CUTLASS_HOST_DEVICE
    PredicatedVectorAccessIterator operator++(int) {
        PredicatedVectorAccessIterator self(*this);
        operator++();
        return self;
    }

    /// Increment and return an instance to self.
    CUTLASS_HOST_DEVICE
    void advance() { iterator_.advance(); }

    /// Returns whether access is valid or not
    CUTLASS_HOST_DEVICE
    bool valid() { return iterator_.valid(); }
};

////////////////////////////////////////////////////////////////////////////////

}  // namespace threadblock
}  // namespace transform
}  // namespace cutlass
